When an addictive behavior is stopped or an addictive
substance is withdrawn from use, withdrawal symptoms almost always follow.
Depending on the behavior or substance, these symptoms can appear within
a few hours (nicotine) or over a few days or weeks (alcohol, or most behavioral
addictions). (Note that the following descriptions apply to both substances
and behaviors.)

Symptoms themselves vary significantly from addiction
to addiction, but there are some commonalities. Withdrawal from addictive
substances is typically followed by anxiety and craving, while behavioral
withdrawal is marked by a need to continue the behavior despite reason or
logic.

Withdrawal symptoms may vary from individual
to individual for the same substance. Some people are able to quit smoking
"cold turkey," (i.e. immediately, without any tapering off), while others
may never find success despite repeated efforts. The length of time and the
degree to which an addict has been involved with a substance is also an indicator
of the severity of withdrawal.

Withdrawal is a more serious medical issue for
some substances than for others. While nicotine withdrawal, for instance,
is usually managed without medical intervention, attempting to give up a
benzodiazepine or alcohol dependency can result in seizures if not carried
out properly.

One of the primary agents in withdrawal is the
brain chemical dopamine. When humans engage in a pleasurable activity, one
physiological reaction is the release of dopamine in the brain's pleasure
center. Addictive substances such as nicotine and cocaine mimic the class
of brain chemicals known as endorphins which regulate the release of dopamine.
When the effect of the drug wears off and the dopamine level falls, the user
experiences the reduced level as a depressed mood, and will re-use in order
to re-establish, quite literally, a "high."

An interesting side-note is that abstention from
some substances which are generally considered highly addictive may not result
in withdrawal. There exist documented cases of soldiers returning from Vietnam
with heroin addictions. Once home, with the pressure of war behind them,
they were able to leave the heroin behind as well (see Rat Park for experiments
on rats showing the same results).

Concerns over withdrawal are not limited to
substances or activities normally considered addictive. Persons who require
antidepressants, for instance, are not addicted to them in the technical
sense, yet abrupt, unmonitored withdrawal from such medications can cause
withdrawal symptoms that have been reported by many patients to be worse
than those from opiates such as heroin or narcotic painkillers.

The drugs Effexor (venlafaxine) and Paxil
(paroxetine), both of which have relatively short half-lives in the body,
are the most likely of the antidepressants to cause withdrawals, but other
antidepressants can as well. Prozac (fluoxetine), with a half-life from 2
days following a single dose, to approximately 9 days for the active metabolite
after multiple doses, is the least likely of the SSRIs and combination serotonin
and norepinephrine acting antidepressants SNRIs to cause withdrawal symptoms.
This long half-life enabled Prozac to also be released as a formulation that
can be taken once a week, Prozac Weekly.

Many substances can also cause rebound effects
(significant return of the original symptom in absence of the original cause)
when discontinued, regardless of their tendancy to cause other withdrawal
symptoms. Rebound depression is common among users of any antidepressant
who stop the drug abruptly, which can sometimes feel worse than the original
state before taking medication. This is somewhat similar (though generally
less intense and more drawn out) than the 'crash' users of Ecstacy, amphetamines,
and other stimulants experience. Occasionally light users of opiates that
would otherwise not experience much in the way of withdrawals will notice
some rebound depression as well. Extended use of drugs that increase the
amount of serotonin or other neurotransmitters in the brain can cause some
receptors to 'turn off' temporarily or become desensitized, so when the amount
of the neurotransmitter available in the synapse returns to an otherwise
normal state, there are fewer receptors to attach to, causing feelings of
depression until the brain re-adjusts.

Other drugs that commonly cause rebound are:

* Nasal decongestants, such as Afrin (oxymetazoline)
and Otrivin (xylometazoline), which can cause rebound congestion if used
for more than a few days

* Many analgesics including Advil, Motrin
(ibuprofen), Aspirin (aspirin), Tylenol (acetaminophen or paracetamol), and
some prescription but non-narcotic painkillers, which can cause rebound headaches
when taken for extended periods of time

With these drugs, the only way to relieve the
rebound symptoms is to stop the medication causing them and ride through
it for a few days, if the original cause for the symptoms is no longer present,
the rebound effects will go away on their own.

As well, many drugs are just not safe to abruptly
stop without the advice of a physician, if the condition they are being used
to treat is potentially dangerous and very likely to return when medication
is stopped, such as drugs for epilepsy, hypertension, diabetes, asthma, and
heart conditions. To be safe, consult a doctor before discontinuing any
prescription medication, unless otherwise directed, or the medication is
taken only occasionally as needed.

The information above is not intended
for and should not be used as a substitute for the diagnosis and/or treatment
by a licensed, qualified, health-care professional. This article is licensed
under the GNU Free Documentation
License. It incorporates material originating from the Wikipedia article
"Withdrawal".